1、BRITISH STANDARD AEROSPACE SERIES BS EN 2437:2002 Chromate conversion coatings (yellow) for aluminium and aluminium alloys The European Standard EN 2437:2001 has the status of a British Standard ICS 49.040 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS EN 2437:2002 This Bri
2、tish Standard, having been prepared under the direction of the Engineering Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 4 January 2002 BSI 4 January 2002 ISBN 0 580 37995 7 National foreword This British Standard is the off
3、icial English language version of EN 2437:2001. The UK participation in its preparation was entrusted to Technical Committee ACE/44, Protective treatments and aircraft finishes, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its s
4、ecretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Stand
5、ards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers
6、to understand the text; present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a fr
7、ont cover, an inside front cover, the EN title page, pages 2 to 9 and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM EN2437 December2
8、001 ICS49.040 Englishversion AerospaceseriesChromateconversioncoatings(yellow)for aluminiumandaluminiumalloys SriearospatialeChromatationjaunedelaluminiumet desalliagesdaluminium LuftundRaumfahrtGelbchromatierenvonAluminium undAluminiumlegierungen ThisEuropeanStandardwasapprovedbyCENon2May2001. CENm
9、embersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisEurope an Standardthestatusofanationalstandardwithoutanyalteration.Uptodatelistsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheManagementCentreortoanyCENmem
10、ber. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlanguagemadebytra nslation undertheresponsibilityofaCENmemberintoitsownlanguageandnotifiedtotheManagementCentrehasthesamestatusasthe official versions. CENmembersarethenationalstandardsbodiesofAustria,Bel
11、gium,CzechRepublic,Denmark,Finland,France,Germany,Greece, Iceland,Ireland,Italy,Luxembourg,Netherlands,Norway,Portugal,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels
12、2001CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.EN2437:2001EEN2437:2001(E) 2 Foreword ThisEuropeanStandardhasbeenpreparedbytheEuropeanAssociationofAerospaceManufacturers (AECMA). AfterinquiriesandvotescarriedoutinaccordancewiththerulesofthisAssoci
13、ation,thisStandardhas receivedtheapprovaloftheNationalAssociationsandtheOfficialServicesofthemembercountriesof AECMA,priortoitspresentationtoCEN. ThisEuropeanStandardshallbegiventhestatusofanationalstandard,eitherbypublicationofanidentical textorbyendorsement,atthelatestbyJune2002,andconflictingnati
14、onalstandardsshallbewithdrawnat thelatestbyJune2002. AccordingtotheCEN/CENELECInternalRegulations,thenationalstandardsorganizationsofthefollowing countriesareboundtoimplementthisEuropeanStandard:Austria,Belgium,CzechRepublic,Denmark, Finland,France,Germany,Greece,Iceland,Ireland,Italy,Luxembourg,Net
15、herlands,Norway,Portugal, Spain,Sweden,SwitzerlandandtheUnitedKingdom.EN2437:2001(E) 3 1 Scope Thisstandardspecifiesyellowchromateconversioncoatingofaluminiumandaluminiumalloys. Itshallbeapplicablewhereverreferenced. 2 Purposeofprocess Toincreasecorrosionresistanceandtoimprovetheadhesionofpaintsandv
16、arnishes. TypeBcoatingsarealsosuitablefortherepairofmechanicallydamagedanodiccoatings. 3 Normativereferences ThisEuropeanStandardincorporatesbydatedorundatedreferenceprovisionsfromotherpublications. Thesenormativereferencesarecitedattheappropriateplacesinthetextandthepublicationsarelisted hereafter.
17、Fordatedreferences,subsequentamendmentstoorrevisionsofanyofthesepublicationsapplyto thisEuropeanStandardonlywhenincorporatedinitbyamendmentorrevision.Forundatedreferencesthe latesteditionofthepublicationreferredtoapplies. ISO8081 AerospaceprocessChemicalconversioncoatingforaluminiumalloysGeneralpurp
18、ose ISO9227 CorrosiontestsinartificialatmospheresSaltspraytests EN2000 AerospaceseriesQualityassuranceENaerospaceproductsApprovalofthequality systemofmanufacturers EN2334 AerospaceseriesAcidchromatepicklingofaluminiumandaluminiumalloys 1) EN3997 AerospaceseriesAluminiumalloyALP2024T3Sheetandstrip0,4
19、mm a 6mm 2) 4 Definitions Forthepurposesofthisstandard,thefollowingdefinitionapplies: batch partstreatedatthesametimeinthesamebath. 5 Classification 5.1 Thickness TypeA:Massperunitareafrom0,2g/m 2 to0,42g/m 2 forslightcorrosionprotection,wherelow electricalresistanceisrequired ; TypeB:Massperunitare
20、afrom 0,42g/m 2 to1,2g/m 2 forgoodcorrosionprotection,withorwithout painting. 1) PublishedasAECMAStandardatthedateofpublicationofthisstandard 2) PublishedasAECMAPrestandardatthedateofpublicationofthisstandardEN2437:2001(E) 4 5.2 Materials Category1:AluminiumalloywithanSicontent 3,5%; Category2:Alumi
21、niumalloywithanSicontent 3,5%. 6 Informationfortheprocessor Designation,see16. Areasnottobechromated. 7 Conditionofpartspriortoprocessing Soldering,welding,mechanicaloperationsandheattreatments(exceptforcoldstorage)shallbecompleted. Thepartstobechromatecoatedafterassembly(e.g.byspotwelding)shallbepi
22、ckledpriortoassembly. Areasnottobechromatecoatedshallbesuitablymasked. 8 Pretreatment 8.1 Cleaning Thecleaningmethodshallbechosenaccordingtothedegreeofcontaminationofthematerialstobetreated. Ingeneral,themosteffectivemethodisdegreasingwithsolventsfollowedbycleaninginanalkalinesolution (seeannexA,A.2
23、). 8.2 Rinsing Thepartsshallberinsedthoroughly,e.g.byimmersionfollowedbyspraywashing.Itisrecommendedthata furtherrinsingbecarriedoutindeionisedwaterwithamaximumspecificconductivityof100 S cm 1 . 8.3 Pickling Itshallnotcausepittingoranyalterationstothemetallurgicalcharacteristicsormechanicalstrengtho
24、fthe material. Thedimensionsandthesurfacesroughnessvalueindicatedonthedrawingsshallbeobserved. Picklingisnormallycarriedoutinasolutioncontainingchromate.Othermethodsmaybeused(see annexA,A.4). 8.4 Rinsing See8.2.EN2437:2001(E) 5 9 Treatment Thepartsaresubmergedinastilloragitatedbathortreatedbysprayin
25、gorbybrushpainting. AnexempleofthepossiblecompositionofthechromatesolutionisgiveninannexA,A.5.However,a commercialproductisgenerallyusedaccordingtothemanufacturersinstructions. 10 Posttreatment 10.1 Rinsing See8.2. Thequalityofthewatershallnotadverselyaffecttheadhesionofpaintsorvarnishes. Rinsinginh
26、otwaterat50Cto60Chelpsthedryingprocessthoughthepartsshallnotbesubmergedfor longerthan1min. 10.2 Drying Dryingmaybecarriedoutatambienttemperatureusingdry,oilfreecompressedairorhotair,atmax.60C. Alternativedryingprocessesarepermissible,providedthattheydonothaveanadverseeffectonthequality ofthechromate
27、coatingandsubsequenttreatments. 10.3 Paintsorvarnishes Theprimerorthevarnishcoatshallbeappliedassoonaspossible(max.48hafterchromatecoating). 11 Removalofthechromatecoating Eitherbyusinganitricacidsolution(e.g.d 1,4)atambienttemperatureorachromicacidsolution (e.g.40g/lto60g/l)at40Cormechanicallybylig
28、htabrasion. Strongalkalinepicklingshallbeavoided. 12 Requirements 12.1 Appearance Thechromatecoatingshallbeiridescentandrangeincolourfromlightyellowtodarkyellowdependingon thetypeofalloy.Itshallbeuniformandfreefromdefects.Powderycoatingsarenotacceptable. Differencesincolourduetodifferentsurfacetextu
29、resarepermissible. 12.2 Massofcoating See5.EN2437:2001(E) 6 12.3 Corrosionresistance Aftertesting,amaximumoffivecorrodingpointsispermissiblepertestpieceandthediameterofeachpoint shallnotexceed0,8mm. Theinspectionshallnotbecarriedoutatlessthan6mmfrom: thetestpieceedges; themarking; themountingpoints.
30、 13 Inspectionandtestmethods 13.1 Parts Eachbatchshallbesubjectedtoavisualinspectionwiththenakedeye. Thenumberofpartstobetestedperbatchshallbeagreedbetweenthepurchaserandprocessor. Forpipes,theinspectionshallbecarriedoutusingeitheranendoscope,oracrosssectionataposition wherethegeometryistheleastfavo
31、rable. 13.2 Testpieces Thequalityofthechromatecoatingshallbecheckedregularlyandatleastonceeverythreemonthsonat leastthreetestpieces: inaluminiumalloyEN3997unplated; dimensions:75mm 250mm 0,8mmto1mm. 13.2.1 Massperunitarea SeeISO8081. 13.2.2 Corrosionresistance Chromatecoatedtestpiecesshallbe: agedfo
32、ratleast24hatambienttemperature; exposedtoacontinuoussaltspraytestaccordingtoISO9227atanangleofinclinationof6tothe perpendicularline: thicknesstypeA: 72h; thicknesstypeB: 168h; rinsedincold,runningwater,toremovesodiumchlorideresidues; airdried. Inspectionshallbemadevisually. 13.3 Baths Thesolutionsh
33、allbecheckeddaily,priortouse,forliquidlevel,cleannessandtemperature. Chemicalanalysesshallbecarriedoutontheconstitutionofthebathandatregularintervalsduring operation.Afreshpreparationisrequiredifcorrectionsremainineffective.EN2437:2001(E) 7 14 Qualityassurance 14.1 Approvaloftheprocessor SeeEN2000.
34、14.2 Processapproval Theprocessorshallcarryout: chromatecoatingonaseriesofpreproductionpartsmadeupofthefirstbatchoftheparts; testsspecifiedinthisstandard,unlessotherwiseagreedbetweenthepurchaserandprocessor. Whenthetestresultshavebeenacceptedassatisfactorybythepurchaser,heshallgivehiswrittenapproval
35、 tostartproduction. Theprocedureshallnotbechangedwithoutpreviousagreementfromthepurchaser. 14.3 Acceptance Thefrequencyandnatureoftheinspectionofpartsandtestpiecesshallbedefinedinthedefinition documentsordeterminedbyagreementbetweenthepurchaserandprocessor. Thepartsshowingdefectsonvisualinspectionsh
36、allberemoved.Faultyareascanonlybetouchedupwith thepurchasersagreement. 15 Health,safetyandenvironmentalaspects Locallyapplicableregulationsandlawsshallbeobserved. 16 Designation EXAMPLE: Identityblock EN2437A2 Numberofthisstandard Type(see5.1) Category(voir5.2)EN2437:2001(E) 8 AnnexA (normative) Rec
37、ommendationsforsurfacepreparation A.1 Scope Thisannexdescribessolventsandbathpreparationaswellasprocessesforcleaning,picklingandyellow chromateconversioncoatingofaluminiumandaluminiumalloys. Allprocessesprovidingresultswhichareatleastequivalenttotheonedescribedmayalsobeapplied. A.2 Degreasing A.2.1
38、Inorganicsolvents Thisprocesscompriseshotorcolddegreasingatliquidorvapourstatewithauthorizedproducts. A.2.2 Alkalinecleaning Thisprocessmaybeusedeitheraloneorinadditiontodegreasingwithsolvents.Inhibitorsshallbeaddedto thedegreasingbathsinordertopreventthemetalsurfacesfrombeingattacked.Theycanbeusedi
39、nahot orcoldstateandwithorwithoutelectriccurrent. A.3 Cleaningbyabrasiveblasting A.3.1 Coarsecleaning Thistypeofcleaningisachievedbymeansofblastingwithagrainsize 100 m,withorwithoutwater. Thisprocessisnotapplicabletothinpartsorpartswithlowsurfaceroughness. A.3.2 Finecleaning Thistypeofcleaningisachi
40、evedbyblastingwithagrainsize 100 m,withorwithoutwater. Aftercleaningremoveanyblastingmediumstilladheringtothepartsanddecontaminatethepartsbysuitable pickling.EN2437:2001(E) 9 A.4 Pickling A.4.1 Acidpickling A.4.1.1 Acidchromatepicklingforclass1materials SeeEN2334 A.4.1.2 Otheracidpicklingmediaformat
41、erialsofclasses1and2 Commercialorotherproducts,e.g.thosecontainingfluorides,maybeused. A.4.2 Alkalinepicklingforclass1materials Thisprocess,basedonsodiumhydroxideshallnotbeusedforpartswithclosetolerancesorforparts fastenedbyrivetsorspotwelding.Moreover,itincreasessurfaceroughness. Thedegreasedmetali
42、simmersedinthefollowingsolution: Sodiumhydroxide : 26gto50g; Sodiumheptonateorgluconate : 0,75gto1,0g; Temperature : 40Cto65C. Thereactionisverystrongandnormallyanimmersiontimeof15sto1minissufficient. Therateofremovalbythealkalinebathis0,6 m/minto1,5 m/min. A.4.3 Desmutting Thefilmremainingafterakal
43、inepicklingandsomeacidpicklingprocessesshallberemovedbyimmersionin asolutionof30%to50%byvolumeofnitricacid(d 1,4)atambienttemprature. A.5 Chromatecoating Thefollowingpreparationmaybeusedasthebathsolution: N a 2 Cr 2 O 7 .2H 2 O : 7,5g/l; NaF : 1g/l; K 3 Fe(CN) 6 : 5g/l; HNO 3 : 1,15g/l; Water : maximumspecificconductivity100 S cm 1 ; pH : 1,2to2,2; Solutiontemperature : 15Cto55C; Treatmenttime : 5sto8min.BS EN 2437:2002 BSI 389 Chiswick High Road London W4 4AL BSI British Standards
